1. Field of the Invention
The present invention relates to flat panel display devices, and more particularly to a field emission display device enabling a uniform dispersion of electrons.
2. Description of Related Art
Display devices have become increasingly important in modern life, where televisions, cellular phones, personal digital assistants (PDA), digital cameras, and personal computers and the Internet, rely on controlling displays to transmit information. In contrast to the traditional Cathode Ray Tube (CRT) displays, flat panel displays are superior as far as being lightweight, compact and friendly to human health. However, there are still problems to be solved in terms of viewing angle, brightness, power consumption.
Among newly developed technologies for flat panel displays, a field emission display (FED) has its special merit of high definition, equal to a CRT display, and unlike liquid crystal displays, does not have drawbacks in a narrower viewing angle, a smaller working temperature range, and a slower reaction. The FED has advantages in high production rate, a short response time, an excellent displaying performance, a brightness over 100 ftL, a lighter and thinner structure, a wide viewing angle, a greater working temperature range, and a higher action efficiency.
Further, an FED does not need a backlight module, and as such, an outstanding brightness can be obtained even under outdoor sunshine. Following developments of nanotechnologies, considerable emphasis has been placed on research of new materials which are introduced to electronic emission components. A carbon nanotube-field emission display (CNT-FED), which applies a theorem of point discharge, takes the place of an electronic point emission component. As a result, an FED has been considered competitive with an LCD, or even a substitute for an LCD in the future.
The working theorem of an FED is similar with that of a traditional CRT, where a luminescence is produced when electrons are “pulled out” by the points of cathode electrodes in an electric field of 10−6 torr vacuum condition, and are accelerated by a positive voltage of an anode plate so as to bombard a fluorescent material on the anode plate. Accordingly, electric field strength affects directly the number of electrons emitted from the cathode electrodes. In other words, the greater the electric field strength is, the higher the number of electrons emitted from the cathode electrodes. Consequently, in the case where the electric field strength fails to disperse uniformly, a problem of non-uniform elevation for the dispersion of electron emitters will result.
In a low-cost traditional screen-printing process, materials can take a formation only under a high-temperature sintering. Nevertheless, the materials subject to the high-temperature sintering are not able to form layers of even surfaces, or most likely collapse or deform. As a result, emitters formed on the surfaces of the cathode electrodes have a non-uniform elevation due to the problem of uneven surfaces of cathode electrodes.
Since every pixel of an FED possesses itself a corresponding field emission array, a non-uniform elevation of electron emitter dispersion will result in a problem of non-uniform electric field strength of inductance, and so cause non-uniform electron emitting density. This will result in an FED of non-uniform brightness, low contrast, inferior production rate and poor image quality of screen.
To solve the problem of non-uniform elevation for the dispersion of electron emitters, conventional art adds a surface-flattening process during a screen process and after sintering of materials among layers so as to obtain a structure of even surfaces on layers. In spite of the fact that through this process the above-mentioned problem can be solved, cost in making FEDs has been raised simply because of such a complex process.
Given the above, an FED of uniform dispersion of electron emitters is presently an urgent need, which not only makes a uniform dispersion of the electric field, but also results in a uniformity of electron emitting density, and thus provides a screen of high quality image.